The present invention relates to apparatus for obtaining pure water from crude water, and more specifically to such apparatus that include an evaporator arrangement having a first circuit for circulating crude water, a second circuit for circulating liquid coolant. Pure water is obtained from the crude water through the medium of membrane distillation.
The present invention relates to apparatus for obtaining pure water from crude water, and more specifically to such apparatus that include an evaporator arrangement having a first circuit for circulating crude water, a second circuit for circulating liquid coolant, and membrane elements for separating the circulating crude water from the circulating liquid coolant and for obtaining pure water from the crude water through the medium of membrane distillation with the aid of the membrane elements that delimit the circulating crude water.
It is known to purify water by means of different kinds of distillation processes, and it is also known to obtain fresh water from salt water for instance, by membrane distillation. See, for instance, Swedish Patent Specifications 408037 and 411446 in this regard.
Swedish Patent Specification 448085 expresses the aim of utilising the energy delivered to the process to a maximum. The process uses a membrane-equipped distillation unit, a first unit which functions to heat water to be distilled and to lead said water to one side of the membrane, and a second unit which functions to lead water that is colder than the first mentioned water to the other side of the membrane. The two units are interconnected by means of a connection line, such that water is transferred from the second unit to the first unit either intermittently or continuously. The water is heated to a requisite temperature in the first unit, by causing said water to flow via a heat exchanger that is connected to an energy source. Energy is transferred from the second unit to the first unit, by means of a heat pump and two further heat exchangers.
Access to drinkable water is a vital necessity for the survival of all mankind. Unfortunately, however, the natural availability of drinkable water differs significantly in different parts of the world. In places where the supply of drinking water is insufficient to meet prevailing needs, it is necessary to produce drinking water artificially, and at a price which is reasonable for the people and the places concerned.
Many of the processes, apparatuses and devices earlier used to produce drinkable water from salt water for instance are encumbered with drawbacks. For instance, such processes and apparatus are highly energy consuming, generate disturbingly high sound levels and produce water that has an excessively high temperature, all of which results in a liter price that is too expensive for many people.
The object of the present invention is to endeavour to eliminate these and other drawbacks to the greatest possible extent, and, as a result, to provide an energy-lean apparatus which operates at a low sound level and which will produce clean water at a suitable drinking water temperature of about 8-10xc2x0 C.
According to the present invention, an apparatus of the aforesaid kind that includes an evaporator arrangement, a first circuit for crude water and a second circuit for liquid coolant, for obtaining pure water by means of membrane distillation and includes a heat exchanger which functions to raise the temperature of the crude water prior to said water entering the evaporator arrangement, said first circuit being connected to one side of said heat exchanger, and further includes a heat pump which functions to lower the temperature of the liquid coolant prior to said coolant entering the evaporator arrangement, wherein the high temperature side of said heat pump is connected to the input side of said second circuit via the remaining side of said heat exchanger and a cooling device, and wherein the low temperature side of said heat pump is connected to the output side of said second circuit.